text: The sigma hole formalism has been applied to a wide range of interactions involving electrostatic and dispersive attraction between positively and negatively charged sites. These interactions are typically classified according to the identity of the atom that hosts the positively charged site. Interaction types that are broadly accepted as subclasses of the sigma hole interaction include tetrel bonding (in which a sigma hole resides on an atom of group IV), pnictogen bonding (group V), chalcogen bonding (group VI), and halogen bonding (group VII). 
  It remains a matter of some debate whether hydrogen bonding is best classified as a sigma hole interaction, in which the sigma hole lies on the Hydrogen atom, or as a distinct class of interactions. While hydrogen bonds and sigma hole interactions of groups IV-VII both exhibit directional preferences towards linearity, the ability of hydrogen bonds to deviate from an ideal 180° angle is much greater.  On the other hand, it has been argued that the underlying mechanism dictating both interactions is identical, and the observed difference in orientational preference can be attributed to a difference in the shape of the sigma holes.